The present invention relates generally to multi-emitter laser modules with optionally an integrated cooling system.
Single semiconductor lasers or emitters are compact and are widely used in a wide range of applications. In some applications an optical output power is required that is significantly greater than the output of a single emitter. One solution is to create a module with a plurality of single emitters and to combine the optical output of the individual single emitters into a combined optical output. The term single emitter is used herein. An example of a single emitter is for instance the L4 diode laser module by JDS Uniphase Corporation. However, a source of laser radiation can also be a stack or an array or bar of semiconductor lasers or a plurality of laser diodes. An example of a laser bar is the TruDiode 301 by TRUMPF. Both the single emitter, which is a single laser diode, and a stack or bar of laser diodes or a plurality of laser diodes will be considered herein to be a single laser source, unless specifically identified differently.
Multiple laser sources can typically be assembled in a module such that the individual beams of the single sources are optically stacked in one axis to generate a single beam of laser radiation with a much higher optical power level than from the single laser source. Polarization and wavelength combining are often used in addition to optical stacking to further increase the optical power and brightness. There are different known ways to position individual laser sources in a module and combine the individual outputs into a more powerful combined optical output. See, for example, U.S. Pat. Nos. 7,801,190 and 8,611,389.
Edge emitting laser diodes are known in the art. For illustrative purposes a diagram of such a laser diode 100 is provided in FIG. 1. The diode contains multiple layers, including P and N layers and a radiating layer 101, generally with a long body and a smaller facing side. The identified aperture or facet of the layer 101 is the radiating part of interest of the device 100. Generally, the emitting apertures of a laser diode are rectangular in shape with the long dimension having a size of typically tens to hundreds of microns, while the short dimension is typically one to two micron in size. Diffraction effects cause the emerging radiation to diverge, with the divergence angle being inversely proportional to the size of the aperture. The short dimension of the aperture s comparable to the typical laser diode wavelength of approximately one micron; diffraction effects result in large beam divergence in this, the “fast axis”, direction which may be as high as seventy five degrees. The size of the divergence angle is known as the numerical aperture (NA), the beam having a lower numerical aperture along the direction of the stripe than perpendicular to the stripe. The long dimension of the stripe is known as the slow axis of the laser diode.
Collimating lenses are applied to correct for the divergence of the radiation in the direction of the fast axis and the slow axis. In general, the fast axis collimators are placed directly or close to the output of the laser and may be cylindrical or toroidal in shape. At a further distance than the fast axis collimators, a slow axis collimator is applied to each laser source. Accordingly, the output beams of the individual laser sources are typically all collimated before being combined. The collimated individual source beams then have to be combined with an optical combiner into a single output beam, by for instance an optical multiplexer or by a polarizer.
In order to be able to properly collimate the individual beams and properly align the beams to enable combining, the individual laser sources have to be arranged and aligned with optics to keep individual beams separate and limit cross talk and interference of individual beams before the combining step.
The related art provides several approaches to the creation of a combined laser beam in a laser module using single emitters. U.S. Pat. No. 8,437,086 issued on May 7, 2013 to Du et al. and which is incorporated herein by reference in its entirety, shows several approaches and configurations of carriers, integration and lay-out of optics and devices. It also demonstrates some of the issues inherent in the approaches taken. The apparatus that contains the individual single emitters and combines them into a single optical output will be called a multiple laser module or just module.
Accordingly, improved and novel multi-single laser emitter modules with cost effective architectures and housings, are needed.